A set of tape guides are usually provided to guide a running tape so as to prevent the tape from vertically moving on the face of the head and is usually formed as integral parts of a magnetic head. A conventional magnetic head having a set of tape guides are shown in FIGS. 14 and 15, which comprises a head main body 101, a head holder 102 supporting the head body 101, and a set of tape guides 103,103 each having a slope 106 at its bottom inclined at an angle of .alpha., whereby a running tape 109 is pressed upward against restrictive members 105,105 to restrict the vertical displacement of the tape. Such tape guides are disclosed in Japanese Utility Model Application Laid-Open No. Sho 60-67535 and Patent Application Laid-Open No. Sho 57-186258. The former has its restrictive members 105,105 formed integrally with the tape guides 103,103 of the head holder 102. Although not shown in the figure, the restrictive members 105,105 of the latter are made of a spring member and are independent of the head holder 102.
If the attachment of these heads to a magnetic recording/reproducing system is somewhat deviated from the proper attachment direction at an angle, the tape 109 may run at an right angle with respect to the head gap G when said angle is within a certain range. If the attachment is deviated by a great margin, or at an angle of .theta.' as shown in FIG. 15 exceeding the allowable limit, the force applied by the sloped section 106 on the tape 109 alone is not sufficient to compensate the displacement caused by inclination at .theta.'. As shown at the upper right in the figure, the tape will be unable to run along the predetermined position as it deviates from the restrictive member 105 of the tape guide 103. As a result, when the angle of displacement .theta.' is about .+-.50' with respect to the predetermined attachment angle (standard attachment angle), the azimuth is substantially out of registration and the output is lowered.
Conventionally, it has been proposed to increase the angle of inclination .alpha.. The angle may be increased to 40.degree.-60.degree. at best as in the prior art, and if the angle exceeds the limit, the tape would be more likely to curl, causing gap loss. That is, the tape would come off from the gap and the output is lowered. Particularly when the base of the tape is thin, the effect of the gap loss is so great that the tape becomes practically unusable.
Moreover, conventional tape guides 103,103 are generally made of plastic by a method such as injection molding. However, the contacting face of the restrictive member 105 against which one edge of the magnetic tape 109 slides is subject to a very high pressure in terms of a force per unit area, even if the force of the sloped section 106 forcing the magnetic tape 109 upward is small since the contact area is extremely small. In addition, as the tape is running while in constant contact with the member, wear of the restrictive member cannot be ignored in practice.
In order to overcome the problems, glass fiber or carbon fiber of 50-100 .mu.m (limit) in length was added to the base resin in the prior art. However, the filler was too long, and the resultant surface was never smooth enough. Although the strength of guides may increase by the addition of the filler, there were other problems such as the loss of magnetic powder from the tape or uneven wear at the guide portions.
Japanese Patent Application Laid-Open No. Sho 59-207050 discloses a magnetic recording/reproducing device for video images in which the tape guides are made of polyacetal resin, polybutylene terephthalate resin or polyethylene terephthalate resin blended with fibers of potassium titanate at a weight ratio of 5-30%, the fiber having the diameter of 1 .mu.m or less, length of 5-100 .mu.m and the ratio of length L against diameter D, L/D=10-200. The tape guides have a good slidability which is comparable to one of tape guides made of hard chromium-plated stainless steel.
Unlike the head for video image recording, audio tape recorders may be mounted on an automobile wherein during the midsummer the temperature would rise as high as 80.degree. C., and reliability at high temperatures becomes critical.